Winter, Spring, Summer, or Fall: Does Season of Birth Affect the Risk for Developing Allergies?

Since many of your little ones have food allergies and related allergic conditions, we like to keep you updated on relevant research results.

Spring pollen is nothing to sneeze at

One recent study1 found a link between persistent pollen exposure during infancy and the development of allergic disease, specifically  asthma and hay fever.

The increased risk was found for babies exposed to pollen during the first 6 months of life. The association between pollen and allergy was strongest when pollen exposure occurred during the first 3 months of life. This suggests – but doesn’t prove – that babies who experience their first pollen season prior to 6 months of age may be at greater risk of developing asthma and hay fever than babies who don’t.

Pollen levels are usually highest in spring. Babies born during winter and spring are exposed to more pollen during their first 6 months than babies born during summer and fall.

Remember that an “increased risk” does not mean that high pollen exposure causes asthma and hay fever. Many babies born in winter and spring DO NOT develop those allergies. Also, many babies born in summer and fall DO develop them. However, these findings suggest that being exposed to high amounts of pollen during the specific window of 0-6 months of age may contribute, along with various other environmental factors and genetics, to the development of certain allergic conditions.

Keep in mind that pollen levels vary from place to place. The amount of pollen in the air tends to be higher in warm, dry climates, and lower in cool, rainy climates. Therefore, babies living in warm, dry areas will be exposed to more pollen than babies in cool, dry areas, regardless of season.

Don’t fall out of your chair

Recently, researchers in the United Kingdom looked at the influence of birth season on allergic outcomes. They also found a link, but their results were different.

This team looked at children under 18 years from the Isle of Wight. They compared their birth season, several other factors, and allergic outcomes. They found that children born in fall had an increased risk of eczema compared to children born in spring. They further linked the risk to genetic factors that happen after birth which can be influenced by the environment.

Shining light on winter darkness

In most parts of North America, winter time means shorter days. As the sun drops lower in the sky and we wear more clothes, we get less UV-B (sun) exposure and hence make less vitamin D. A few years ago, researchers asked whether this might have a link to good allergies.

we wear more clothes, we get less UV-B (sun) exposure and hence make less vitamin D. A few years ago, researchers asked whether this might have a link to good allergies.

Researchers in Boston compared people who went to the hospital for food-allergic reactions to children who were hospitalized for other reasons. They looked for an association with birth month. What they found might surprise you.

Of over 1000 patients with food allergy, they found that younger children (under 5 years) were more likely to have been born in fall or winter months. This link didn’t hold up for older children and adults. The link also didn’t hold up for children who came to the hospital for non-food allergy reasons.

The takeaway? Children in Boston under 5 years born in fall or winter had a higher likelihood of food allergy. The authors suggest this might be influenced by seasonal differences in sunlight exposure.

So, can the season of birth affect the risk for developing allergies? The short answer is that it may, given the links these research teams found between, spring, fall and winter births and various allergic conditions. This is just a snapshot: research has also found associations between other environmental factors that can vary with seasons in infancy and other allergic conditions. It may turn out that every season has it’s own link to allergic conditions!

Pretty interesting, isn’t it?

Mallory West

[i] Erbas B, et al. Persistent pollen exposure during infancy is associated with increased risk of subsequent childhood asthma and hayfever. Clin Exp Allergy 2013 March;43(3):337-343.

Published: 05/16/2013
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